It is proposed to carry out an analysis and comparative study of the motor potential in monkey and man. This potential was first discovered in recordings from the human scalp (Kornhuber and Deecke, 1965; Vaughan, et al., 1965) where it was shown to precede (by 1-2 sec.) the onset of movement with which it was associated. In the context of this proposal, motor potential denotes a slow (several seconds) potential recorded directly from the cortical (cerebrum) surface or epidurally during a learned or active movement. In man, recordings are made before and during operations for epilepsy and the recording electrodes are the same surface electrodes as those used to localize the epileptogenic focus. In the monkey, both transcortical and monopolar recording is used. In both animal and man, recordings are made simultaneously from multiple (6-7) areas. We wish to determine the following: the various cortical areas that become active during movement and the sequence in which the different areas are activated, information which may help answer where in cerebral cortex learned or voluntary movement is initiated; the difference in distribution of potential to active movements and those carried out passively; the difference in distribution between motor potential and electrically excitable (for producing movement) cortex; relationship of magnitude of motor potential to the force of the movement; comparison of topographic distribution of motor potential between monkey and man. In monkey carry out experiments to assess the cellular elements which generate the extracellular current flow giving rise to the motor potential, i.e. sustained synaptic activity, glial depolarization or both. The studies should contribute towards understanding the physiology of willed movement.